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Air Traffic Control System management
I'm having a class about Database management system, and the professor gave us a project regarding Air traffic control system. The exact assignment is to "Design and create a system which can manage informations of Air Traffic Control System, summarize entities and how system works".
I'm not asking you to do this for me, what I would like to know is

what should i know about air traffic control systems?
how does it work?
what are the entities involved in it?
what is an air traffic control system?

The Air Traffic Control System is extremely broad. It might be better to restrict yourself to a simplified form of the Flight Data Processing System. On wikipedia you'll find a basic introduction

Were you not given more specific direction from your instructor? Reverse-engineering ATC operations is well outside the scope of a database class. You should have been given a schema or specific lists of information to be manipulated for your project. If not you may wish to talk to your instructor to nail down exactly what you're supposed to do, because I'm sure they didn't intend for you to have to learn the intricate inner workings of ATC.

possible duplicate of Where can I find Air Traffic Control information material suitable for beginners and students?

This does seem like an overly-broad assignment - ATC is a lot more than just a database (there's a LOT of logic and constraints when you look at the real system, and that's only considering what the ATC Computers deal with, not the external stuff Pilots and Briefers bring into the process). It sounds like a very interesting project though - more fun than "Build a supermarket inventory system" (the classic DB project when I was in school).

Thank you for your help, even professor doesnt know what he wants, he says do everything what i thought to you, so i will start with ER diagram and database entities, but what are the entities involved in it?

@washaq the simplest entity-relationship model is Airplane & Airport (a "route" in that system is an airplane, a departure airport, a destination airport, and a list of airports over which it will pass; More complex modeling would include "navigational aids" (things that aren't airports over which an airplane may pass), information about the aircraft's speed, estimated departure time, arrival time, and times crossing waypoints (airports/navaids/etc) - There's WAY more to real-world ATC but I'd consider that "adequate" for a school project unless you're studying to be an ATC specialist :-)

Air traffic control system is the computer system that air traffic controllers use to keep track of the aircraft they are controlling.
The system processes data from the primary and especially a secondary radar and displays them in suitable fashion for easy understanding by the controllers. The radar processing itself is not interesting for database class. But there is a bunch of information about each aircraft that needs to be remembered and associated with it's radar image:

The assigned transponder 4 octal digit code (usually called "squawk"). This is a code the secondary radar receives from the aircraft used to associate the data to the correct radar return.
Identification, also used as callsign. It is registration number or flight number (sometimes internal company flight number that is different from what they show in time tables)
Aircraft type

The aircraft type is needed so the controller knows the performance of the aircraft, so it needs associated performance data like maximum speed, approach speed, maximum altitude etc.

Flight plan. This needs to contain:

Start and destination airports
Preferred cruise altitude and speed
List of waypoints

You may consider current clearance limit (altitude and waypoint); I am not sure whether the current systems include it or not.

The Host also keeps track of airspace restrictions so that flights don't get scheduled through restricted airspace. as well as all existing waypoints and data about them as well as sector boundaries....  Its a very complicated system.

As @DavidWilkins points out there's a lot more to what the Host (and ERAM) systems do than what's above, though I would certainly think Jan's answer is more than enough work for a college project. If you really want to dive deeper The FAA Air Traffic Control Plans and Publications are a good resource.

Thank you for your help, as much as i understand that in my project i should involve;
-Squawk code
-Callsign (not internal company number)
-Aircraft type
+Speed
+Altitude
+Type (cargo, commercial, military)
+Available seats
-Flight Plane
+ Destinations
+ Preferred Altitude and speed during flight
+ List of Waypoints (i have no idea about this)
shall i involve airports, people(passenger, flight crew, pilots), etc ?
i think for radar image it should be stored in graph atabase, am i wrong?

ATC doesn't generally care about "people" (other than who the pilot is) - you can use the standard flight plan form for reference, and just strip out a lot of it for the sake of simplicity. The list of waypoints("route of flight") can likewise be simplified (see my comment on the question) - lat/long coordinates or just "flying over these airports" is enough for school projects I think.

Re: RADAR, this actually isn't stored in the ATC computer (there's some information in that computer that is fed to the radar display but if we're simplifying let's ignore all of that). The radar data is essentially a real-time display, and while the FAA records it that's not something that gets "queried" for flight plans and such - if they need historical radar data they get the tapes (probably all electronic now, but it's effectively "tape", it wouldn't be part of what the flight plan & routing computers deal with.

@voretaq7 thank you for your support, in my project i used 3 main objects Plane, GPS, Radar and more ten others Flight file, ground control, air port, ramp control, gate control, etc.
in my project gps locate aircraft, and gives info to plane, plane communicate with radar that plane getting in sector, and all info including wheather goes to central control, and central control navigates aircraft to change route or  asc, desc to avoid possible crash on air.
i think for simple project this is enough.


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What is a 5 Tube System?
I've been going over the new Master Minimum Equipment List (MMEL) for Textron Aviation Model 500 Series Citations and on page 70 an Electronic Flight Information System (EFIS) 5 or 3 Tube System is mentioned but I can't find any information or pictures of it online.
Can someone explain?

Look for the Honeywell Primus 1000 System.
Early systems were 5 tube - an EADI and EHSI for each crew plus an MFD (Nav/Wx display) as shown below:

source: swaviation.com
Later ones were 3 tube - 1 PFD on each side plus the MFD as shown below:

source: airliners.net
The symbol generators are shown in the MMEL as they have reversion capability. The 'tubes' or the actual displays would be listed under section 31 Indicating/Recording Systems but aren't included in the MMEL as they are always required.
Section 34 Navigation does allow for functional portions of the displays to be inop.

If you look at the document you link, you'll see that the 5/3 Tube systems are not EFIS, but "Symbol generators for EFIS":

Looking for "Symbol generator for EFIS" I find the following:

A Symbol Generator (SG) is the device that receives the data from the airframe sensors and serves as the television transmitting station by processing the data for appropriate viewing.
Aircraft with a five-tube EFIS will typically have three Symbol Generators. One will operate the pilot's EADI and EHSI, a second will perform a similar function for the co-pilot's information. The third Symbol Generator provides for the MFD. In the event of a system malfunction, a method of electronic substitution is frequently included. This enhances troubleshooting the system by supplying a second data source to the flight deck displays.

This leads me to believe that "tube" is short for "cathode ray tube".

Interesting. How would a Universal Avionics EFI-890R EFIS be classified then?

@PIXP no idea, that's not my field. sorry

source: Stack Exchange

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sort: votes


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What triggers the trim horn and the "stabilizer motion" aural callout on the MD80?
I got conflicting or incomplete responses from various sources:

There is an internal rate monitor looking to see the stabilizer is
  actually moving .08°/sec or -08°/sec.

https://forums.tfdidesign.com/index.php?/topic/2509-bbetty-stabilizer-motion-warning/

The trim horn will sound each 1/2 degree of constant pilot use, but
  the stabilizer motion call will sound when the auto pilot moves the
  trim 2 degrees within 30 seconds.

https://forums.x-plane.org/index.php?/forums/topic/123539-cockpit-sounds/

The CAWS will provide an aural warning (tone and voice) when the
  horizontal stabilizer deviates one degree or more for a given length
  of time. The warning will be on until the horizontal stabilizer sensor
  goes off.

https://www.airliners.net/forum/viewtopic.php?t=751253
Which one is correct?

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What would escorting an airliner which is the subject of a security threat by fighter jets achieve?
Today, a Ryanair flight from Lithuania to London Luton was the subject of a presumed hoax, and had some form of security alert. In the incident, it was diverted to Stansted, while being escorted by fighter jets.
What would the escort actually achieve? My best guess is to shoot it down in case of a hijacking, but this seems like a particularly grim prospect and perhaps maybe not one that would be so publicly on display. Is there another reason why it might have been escorted?

There are multiple reasons:

Yes, they'll shoot the aircraft down if deemed necessary. It is a grim prospect, but sometimes grim events require grim responses - there is little doubt that many lives would have been saved had the 9/11 aircraft been shot down prior to them hitting the WTC's.
It's a threat and a show of force. Not all hijackers / criminals / terrorists are keen on the idea of losing their life. For those, the threat of being shot down can contain the situation and give some control. If nothing else, being shot down would prevent their political message from getting out - you can't really negotiate the release of prisoners (Or whatever) if you're dead on a blown up plane.
The fighters can get up close and personal with the aircraft. This allows them to see it, see inside and potentially communicate with people on board. During an event where the situation is unclear they may be able to report whether the aircraft is under control and/or command of the pilots.
There are internationally recognised intercept signals that a fighter jet can perform - using lights and motion (Rocking wings etc). This will allow them to pass instructions to an aircraft with no radio capability.

Additionally, escort aircraft can assist the crew of the aircraft.  NASA used to have T-38 aircraft escort the shuttle during the final part of landing.  This was essentially to provide external views and judgement to the shuttle crew.  They would call out altitudes and such.  The same could be useful to a potentially damaged aircraft, or injured crew.

Also the ground would get immediate knowledge on what the aircraft was doing, or if it became damaged in some way.

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How high does a F35B Fighter (whilst hovering) have to be to see the earth rotating at 1000/mph?
Is there a way, or an aircraft that can actually perform this? The F35B fighter jet has hovering capabilities. The only "supposed" images of this 1000 mph spin is from NASA, but the clouds do not move, so it is, in most logic; a computer-animated clip.

I'm guessing that it is the helicopter part that ain't working.

If it is hovering, it does not see the earth rotate, it would defy the definition of hovering.

I was under the impression that it could hover in the air (like in the sky), and not just a couple feet above the ground.

You Aviator guys guys run a hard market :P lol

The definition of hovering is not height-dependent.

Then if the jet is "holding a fixed position" (with help from the north star(?)), a what point/altitude will you see/notice a spin of 1000 mph?

A spin/rotational motion is measured in angle unit per time unit (e.g. degree per second), not in length unit per time unit. See this video.

I'm voting to close this question as off-topic because it would be better answered by Space.SE, since it's about orbital mechanics.

@SteveV. this is not even orbital mechanics: http://aviation.stackexchange.com/a/3426/1467

@Federico - Of course there would be an XKCD for this exact situation.  :]

It seems to me (as a layman, I am neither pilot nor physicist) that if a plane is 'hovering', that no matter the altitude, it will be moving at the same 'speed' as the planet, and hence not see any of Earth's rotation. (By same speed, I mean both 'earth through the cosmos' and 'earth's rotational speed')

It also seems to me (although this one might get me flagged as rude) that the OP is starting to show a habit of asking 'interesting' questions which have problems of factuality (i.e. military over antarctica, planes hovering in space)

You should take this question to Physics SE for a full explanation (which will expand on why it is impossible to define fixed point and stationary and why, in order to see the rotation of the Earth, you must also be moving) and to Sceptics SE for the "supposed rotation" (I don't even know what you're saying here - do you doubt that the Earth rotates?).

I would like to migrate this to Physics SE, how do I do that?

At an absolute fixed position you would see the earth move at 1 inch altitude.  But you would need to traveling 1000 mph relative to the surface of the earth to hold a fixed position relative to the North star.
At lower altitude the atmosphere moves with the earth.  Otherwise we would experience 1000 mph wind on the surface.
There is a spirited debate on fixed position. And this is physics. To me the intent from the OP was clear - take rotation out of the equation.

At the equator hold a position such that you can draw a straight line
between you the rotational axis of the the earth and the center of
the Sun.  To achieve that you would need to travel apx 1000 mph
relative to the surface of the earth and should be able to see that
at any altitude.
Or directly above the axis (north or south) point directly at the Sun. How high would you need to be see the earth spin below you?  I don't think you would see it spin as it relatively low angular velocity (one rotation every 24 hours).

I agree this is not an aviation question. I did not think it would into this level of physics. I am good with it getting migrated. If an moderator wants to delete my answer I am good with that.

[physicist] an "absolute fixed position" does not exist [/physicist]

@Federico And that is why I added  hold a fixed position relative to the North star.

The motion of a point on the equator relative to the North Star is unlikely to be 1000 mph.

@mins unlikely? that's (almost) exactly the equatorial speed around the axis.

@Federico: While it is known the linear speed at the equator is about 1000 mph (relative to the center), the Earth is not fixed relative to Polaris, hence the linear speed of a point on the equator relative to Polaris is unlikely to be the same. For a start the Earth moves around the Sun (66,000 mph relative to the Sun). Also I doubt we know what is our velocity relative to Polaris, as we barely know the distance of Polaris, in the range of 400 l.y. Or am I wrong?

@mins The intent of hold a fixed position is clear enough.

@Blam  The intent of a "fixed position" is only ever clear when the reference frame is also specified.  If you say "fixed position above the Earths surface", then you are only fixed in respect of that point of the Earth.  To everyone else, you are not in a fixed position.  It is just not possible to say a fixed position is clear.  The North Star is also moving, moving really fast, so if you are fixed relative to the North Star, then you are also moving really fast relative to an observer in a different reference frame.

@Simon The fact you say the North Start is not a fixed position means you get the intent.  Come on.  You name the reference - you know the intent.

@Blam: I understand what you mean in the answer, in your effort to clarify things to the OP: the Earth rotates 15° per hour around the pole axis, hence at the equator, with a radius of 6,400 km this translates to a linear speed of 1,000 mph (albeit your answer doesn't mention the equator, at the pole it doesn't work). But talking about being fixed relative to something creates the confusion contrary to what you expected. What you may take as the "fixed" viewing point is, for instance, any point on the line between Earth and Sun.

@Blam Sorry, I don't know the intent at all. Your statement that you would see the earth move at 1 inch if you move at 1000 mph (or whatever the speed at the given latitude, to stay fixed relative to the North Star is nonsense. We don't know how fast the North Star is moving relative to the Earth but it is many orders of magnitude greater, in the order of many 10s of thousands of miles per hour. The North Star only appears to be fixed over small periods of observation. It moves vast distances every day and, in not too long a time, will not even be a useful north (losely) fixed point.

@mins North Star was introduced by the OP to clearly mean not hover with the rotation.  The net is clear.  As soon you hover NOT with the rotation you would see the rotation.

OK, this has nothing to do with aviation.  Please take it to physics SE.

@Blam: Yes, the answer must first explain him that we don't know what is the effect of being motionless relative to Polaris, in the Ecliptic frame. And as Simon says, this  cannot be explained on Aviation without exiting the on-topic scope.

@Simon Then to you my answer is nonsense.  North Star fixed  fixed position was introduced by the OP.  It clearly means a frame of reference removing the rotation of the earth.   The question is closed and I don't think this interaction adds value.

@Simon You migrate questions not answers.  The question is already closed.

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Can excessive G-force break or dislocate bones during pilot maneuvers?
Was wondering if the pilot would faint, could g-force be enough to maybe break the neck bone with the head and weight of a helmet being pulled downwards. Another relay to this is the effects on the inside of the body, more specifically, the brain. Like a boxer, after taking a few too many knockouts. Is there a limit, or an event horizon to permanent brain damage and bone structure deterioration concerning g-force and pilots in aircraft maneuvers?

sounds more like a question for biology.SE

I guess i could specify to fighter pilots. I'm pretty sure airliner pilots don't wear or have a helmet standing by in the cockpit.

What do you mean by "attempting a prone position"? Fighter pilots are strapped into a sitting position.  Yes pilots can be rendered unconscious and can be killed by G-forces. An aircraft with a prone position for the pilot may slightly increase the G that can be withstood by the pilot by reducing the effects of blood pooling in the legs and draining from the brain. But fighter pilots have suits that use pressure to counteract this.

Removed that prone position part. It seemed too long of a question if I were to type the whole brain-damage and bone structure thing.

This isn't exactly a flight maneuver, but using an ejection seat can cause compression fractures to the spine or displace vertebrae due to the high number of Gs (~9g).

No, the moment consciousness is lost, the body will go limp and the hands will release the controls and the aircraft will naturally seek 1g flight.  However, several cases exist where pilots have awoke in a supersonic, or near supersonic, dive and sustained massive flail injuries after ejecting.
Its also important to note that simply jumping in the air will exert your body to instantaneous G-forces well above what you'd experience in a fighter aircraft.  If such G-forces were capable of causing injury then you'd hardly be able to get out of bed without causing grievous injury.
The danger to high G-forces in the vertical axis is that the blood is pulled from the brain to the lower extremities causing a form of hypoxia commonly referred to as GLOC, or G Induced Loss of Consciousness.  For what it's worth, skeletal injuries due to G forces are so rare that they aren't even briefed during training.

Can excessive G-force break or dislocate bones during pilot maneuvers?

Yes.
Even if the pilot remains conscious.
For example see http://medind.nic.in/iab/t00/i2/iabt00i2p1o.pdf which describes compression fractures suffered by pilots.

That report talks about ejections.  I find it difficult to believe that enough G could be exerted to break bones without wrecking the aircraft in any manoeuvring within the envelope.

@Simon: Oops yes, I posted the wrong reference. I'll update the intended reference into the answer. The first case is ejection but some of the others involve high-G maneuvering.

There are no head restraints.  During defensive BFM the pilot has to crain his head around to look behind him while also pulling in excess of 7G's.

Indeed, the G forces generally keep the pilot's head back against the seat - moving it around is quite difficult, and can be painful but it is done under the pilot's control

Yes, there have certainly been cases in which fighter pilots break bones while performing high-G turns. Unfortunately, the bone most susceptible to injury is the spine because that is the one of the few structures supporting real weight other than itself.

...pilots of high-performance aircraft frequently sustained cervical spine injuries due to their exposure to high gravitational forces (5), these investigators measured accelerations about the head of an F-16 fighter pilot during simulated air combat maneuvers. With the aid of a spine model, they calculated the forces on the lower cervical spine and noted that the forces were of the same order of magnitude as failure loads of cervical vertebrae and estimations of maximum cervical spine muscle forces.

In one miraculous instance, a USAF pilot was able to land after pulling a 9G turn and breaking his back. I currently cannot find a source for this but I remember listening to my dad's friends (USN) talk about visiting the pilot. I believe he was disabled in a leg or maybe both but he did not fly again.
Less severe maneuvering will not break bones very easily, but they can produce neck injuries.
There are many safety features built into aircraft that can maneuver into such high-G turns, however. The earliest example of this is the G-suit, which pushes blood that pools in the lower half of the body back up to the brain using air pressure lines and sacs. In addition, some aircraft set artificial limits on how tight a pilot can turn to prevent pilot injury and airframe stress (The F-14 could survive much more than 6-7Gs but that limit was set on the controls to reduce wing stress and failure). More recently aircraft have adopted digital systems that will right an aircraft if the pilot fails to respond to an alarm within a certain period of time. If a pilot is in blackout or prolonged greyout, the aircraft ignores pilot input and tries to fly straight and level. This is mainly to prevent unconscious crashes into terrain, but it also prevents pilots from entering tighter and tighter turns that they cannot leave.

I do this for a living and have yet to hear a single instance of anyone breaking a bone due to G-forces in the jet.  If it happens then its so incredibly rare that its probably a statistical outlier.  I know people that have developed back problems after several years of flying, but I can't think of a single instance where either the total G's, or the onset rate caused the breakage a bone in the aircraft.
There is also no alarm system on any tactical jet.  This would greatly hamper the pilots ability to concentrate on flying the aircraft in demanding flight regimes.

I remember the 9G incident from when I was around 15, so I am recalling that part from distant memory. Sorry, I wasn't clear about the alarm. I am not sure if they have visual cues but I believed auditory alarms were definitely present in military aircraft. Have there not been studies on designing alarms that will not be ignored by pilots, military specifically? However, if you do that for a living, I think you may be a more reliable source. Were you a Phantom Rhino or Hornet Rhino? I always look on with awe when you pilots perform your maneuvers!

There are auditory alarms, "betty" if you will, but nothing that will automatically correct the aircraft.  In fact, there are rare times when the terrain avoidance system actually gets it wrong because we're flying close to the limit. So, especially in those cases, you wouldn't want any automated action to take place.  There may have been studies conducted, but the reality is that any extraneous task (like resetting an alarm) that is taking the focus away from an already task saturated pilot is going to reduce mission effectiveness.  Wow, you certainly know your stuff, I'm a super hornet guy.

It looks like I was confused! Thanks for clearing that up for me; I've never had the privilege to ride in such high-performance aircraft much less pilot one for a living. What I was talking about was likely never used for the reasons you explained.


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How do I obtain the max endurance altitude?
There are excellent explanations of the physics that determine maximum endurance speed here, here, and here.
I was thinking of aircraft that have to be "on station" without an indicated altitude and then wondering: Is maximum endurance not a function of both density altitude and speed?  If so, what are the relevant variables and equations?
(I imagine that maximum L/D is a function of Mach number, so that might conveniently account for the effect of change in air density with altitude.  But from the answers on max endurance speed I see that there are already differences between jets and props which, when air density is added, will result in further differences between turbo-props and piston props.)

Mach number of a function of temperature, not pressure.

Maximum "endurance" IAS can be found found on your rate of descent vs glide speed chart.  Density Altitude and engine selection become critical depending on Mach number (there for altitude) you wish to fly at a given IAS due to the "coffin" corner.  So, if you wish to loiter (other than lighter than air), piston engines will give most power per given unit of fuel. You want low airfoil loading on both your wing and prop to stay away from higher Mach numbers.  The lowly prop driven Helios flew to over 90,000 feet.

The answer depends on many factors. Things to consider are:

Improved efficiency of combustion engines at higher altitude because of lower air temperature.
Lower power output with altitude due to lower air density, so the most efficient power setting coincides with the best endurance speed, which is close to stall speed.

But not all is better higher up:

Again due to lower temperature at higher altitude, the Reynolds number drops over altitude, even when the higher flight speed to compensate for the drop in air density is factored in. This increases the zero-lift drag and lowers the maximum lift coefficient. For propeller-driven high aspect ratio designs this alone lowers the maximum endurance altitude.

There is more, but those are the main factors. So it depends on engine characteristics, wing loading, planform and airfoil and even on atmospheric conditions. This makes it hard to give a generalised answer – in the end the optimum has to be found for each design individually.
With all caveats, a good candidate for the optimum endurance altitude is close to the service ceiling of the aircraft when optimum loiter speed can be flown at the cruise power setting of the engine. If winds allow: A maximum of wind speed occurs near the tropopause, and in order to keep station even in high winds, it might be impossible to fly at best loiter speed. There are stories of Me-109s which should be flown to the western front from the plant in Augsburg and ended up on airfields in Czechoslovakia, because the pilot got caught in the then-unknown jet stream.

Wind speed over altitude at 40N latitude (picture source).

This is a good preliminary answer with some great information.  For the purposes of this question ignore the winds aloft; i.e., loiter location is unimportant.


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What is the cause of the whiny noises in cabin of the Boeing 787?
What are the various whine noises coming from the Boeing 787 cabin? Especially near the wing. I have seen tons of YouTube videos in which it has a noise during takeoff, or when flaps are being lowered or raised?

the flap motors?

Yeah, the noises while the flaps are being extended or retracted are just the actuators for the flaps. During the takeoff run would be something else. The latter might be the notorious supersonic blade tip buzzsaw sound, especially if it's using the Trent engine rather than the GE engine. I've heard that in several Trent-powered 787 takeoff videos.

@reirab, if you watch the first couple of seconds in this video you will here a really high pitch frequency from the 787, what is that actually? link also at 1:32 you here this other noise

@Techno04335 It's probably best if you can keep each question about one particular thing and preferably link a video or two that demonstrates what you're referring to (like you did in the comment,) ideally with the time of the video you're asking about. In general on StackExchange sites, we like to keep each question to just one answerable question.

@casey "The passengers."

@voretaq7 Damn, you beat me to it.

@voretaq7 Not the Cabin Crew?

Other people have complained about this too. Boeing should rename the type to the "Whineliner".
The noise is caused by a hydraulic pump which is situated directly below the cabin. It mostly runs on takeoff and landing, but it can also run automatically at other times.
Dogs have been reported to need psychiatric treatment after being transported on a 787.

If you could maybe provide a source for the last line there...

@KorvinStarmast, I am thanking him for the reply and the description of the hydraulic pump.

This isn't too unusual compared to other airliners eg A330, etc.  The sound comes from the rotary hydraulic motor situated in the wheel well of the jet which turns the drive shaft for the flap drive screw jacks.  This is a typical arrangement for Boeing jetliners.


text:
Does landing in extreme weather conditions require any different or special training?
Is there any special training, relating to land under extreme weather, such as snow storms, contaminated runways or ice conditions?

Typically you don't land on a unsafe runway. Instead you divert to your alternate.

I meant to land, not on an unsafe runway. just to land. For example, the brake´s usage during roll out, the reversers, avoiding deep landings, any technic that may prevent or avoid runway excursions.

Related : Are pilots generally trained for crosswind landings? ---- How does one train for making landings and takeoffs in bad weather? and What kind of aircraft may land on iced areas, like Antarctica?.

On icy runways and taxiways, best to taxi considerably slower than normal, especially when turning. Turns should be made at walking speed to minimize nose gear slippage. On 747-100/200 aircraft if you know you're going to be operating in icy conditions and you have control over the aircraft loading, best to make sure the c.g. is forward of 26.6% MAC to get weight on the nose gear.

In some regards there is but this depends on what you consider extreme weather.
On one hand there are physical limits to which a plane can be landed when it comes to wind both head on and cross winds. Granted they are cases they may never or only rarely come up you may simply not be able to land the plane.
Assuming you have made it to the airport and are able to land...
There are some check lists and different procedures that me be executed for different weather. Snow and wet runways in general may see a longer landing distance and roll out however this is not "special" training as landing distance should always be calculated based on conditions.
Approaches are flown as published but changing winds and weather may cause the pilot to react differently or do different things to fly the approach. For example if you compare a calm wind approach to a dry runway with a wind sheared approach to a wet runway you may see some differences. The pilot may elect to come in a few knots over Vref and possibly with less flaps in a wind shear situation. Again this is not special training as much as it is standard.
On a contaminated runway the pilot may chose to preform something like a short field landing so as not to potentially collapse the nose gear. All pilots (even GA) are trained in this maneuver. There are so many possible situations here it would be hard to train for ever one but some are trained for or a checklist exits.
Side Story: I was talking to a commercial pilot recently who flies the 777 and he was telling me a story of a time during training in the sim where they gave them heavy rain and 40Kts of wind shear (no one could successfully land the plane that day in his group in the sim). So they do at least throw situations like that at pilots in the sim, if they do it all the time I cant say.

As a pilot, you are trained for all eventual failures and conditions, but above all else your priority is the safe operation of the aircraft.
Therefore, landing during hazardous conditions is always avoided as a primary response.
There is nothing special (beyond training in the simulator) that is required to land aircraft in difficult conditions; because the mechanics of landing the aircraft do not change, just the variables you have to account for.
So, as common sense - during rain/sleet/snow/ice - a longer rollout is required to come to a stop. You may also land with extra reserve power in case a takeoff/go-around is required (especially true in high wind / wind shear conditions).
Other than that, there is nothing special about landing in snow/sleet/rain vs. normal conditions.

In commercial pilot training, they have to go through training for all sorts special situations training. Every pilot must go through training for such situation. So it probably is not "special" as requiring a whole new course or something like that although it might be "special conditions" inside the training programme. However, as a comment above said, it would be safer to divert to an alternate airport if possible.


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Is this the shortest route served by an Airbus A320?
Is this the shortest route served by an Airbus A320? Port Louis to Saint-Denis, 231 km (144 mi). Air Mauritius flight MK248.

Looks pretty short to me, are you curious because of the course changes near the airports? Or are you asking if this is historically the shortest route that an A-320 serves?

Basically, both!

This site seems to indicate that they had the shortest route using the A-320 family of aircraft at just over 70km. The page also shows a list of flights, and it looks like one of them is listed at 58km. Based on that list, it looks like your 231km flight wouldn't even break the top 10.

Its difficult to search based on the length of the route and the aircraft type. As far as I can find though, 58km ACE->FUE shortest scheduled route for the A-320.

Who is "they" in your first sentence?

the article topic was about fastJet, so that is the "they", although the chart in the article disputes the claim.

I think it's not in the table because fastJet hasn't started flying the route yet.

Even if it was, it still isn't the shortest, they claim 70km, the shortest in the list is 58, so fastJet would fall in at number 4.

I think the fastJet flight will be the shortest daily service. Further down in the article it talks about how the other short flights are less than daily. I found that confusing too.

Just as side info: The canary islands are quite popular destinations for vacation for Europeans. They fly there mostly with A320 and 737. It seems the aircraft just hop to the next island before flying back.

I'm wondering, if first four aren't simply single operated flight marketed under four different carriers (i.e. code share flight). Seems possible. If yes, then placing these as four different items in list seems a bit confusing, as by single flight I understand single route. But, I may be wrong.

I don't think so. The shortest route with an A319, which is an A320 family aircraft that I am aware of is Dar es Salaam - Zanzibar (HTDA, HTZA) which if I recall is roughly 73 kilometers (probably even less from airport to airport) operated by FastJet Tanzania.
Source here

The shortest A320 route I know of is from Dammam to Bahrain. The flight duration is 15 minutes.


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Is this BA15X flight a logistic flight for British Airways?
Right now (26/11/2015, UTC 17:16), British Airways is flying over the Australian Outback with two Boeing 777-336(ER)s, christened flight BA15 (http://www.flightradar24.com/BAW15/8169bb5) and BA15X, which is slightly ahead (http://www.flightradar24.com/BAW15X/8169237).
Why is this? Is flight BA15X a logistic one? And if not, why did they use an "X" to distinguish between the two instead of another number?
EDIT
I am also wondering: is this going to cost extra money to BA, owing to the new slot they had to purchase or rent for operating a contemporary, second aircraft at SYD?

The Wednesday flight was indeed delayed for a full day as was suggested in a comment.

Is this going to cost extra money to BA, owing to the new slot they had to purchase or rent for operating a contemporary, second aircraft at SYD?

It will cost extra money for the changed/additional slot at Heathrow, for sure. There may be costs at other airports. As to the aircraft, it depends whether BA had another suitable, unutilised aircraft available (this is a fairly quiet time of year, so it's not unreasonable to guess that BA may have had a spare at Heathrow...). But yes, this will (overall) have cost BA some money: any significant delay does


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How to understand US military aircraft designation on the vertical stabilizer?
There are many letters and numbers printed on the vertical stabilizer of US military aircraft. They identify the plane's design and purpose.
What are those letters and the meanings?

I love how "beware of blast" is written small enough that you have to get in real close to read it...

@falstro At least it isn't written on the back of the nozzle...

Isn't that Air France flight 823 for Los Angeles?

The number on the vertical tail is the aircraft serial number, not the type designation. Here the serial number is AF 41 823. The '4' is the last digit of the finacial year in which money was allocated to manufacture the aircraft and the remaining 4 digits represent the sequence number indicating the sequential order in which the particular aircraft was ordered within that particular financial year.
From USAF serials:

Starting on July 1, 1921 (the beginning of FY 1922) a new serial number system was adopted based on procurement within each Fiscal Year. Each serial number now consisted of a base number corresponding to the last two digits of the FY in which money was allocated to manufacture the aircraft, and a sequence number indicating the sequential order in which the particular aircraft was ordered within that particular FY. For example, airplane 22-1 was the first aircraft ordered in FY 1922, 23-1 was the first example ordered in FY 1923, etc. This system is still in use today.

Apparently, USAF decided to have five digits in its tail number in 1958. This resulted in the cutting of first digit of the financial year.

Camouflage began to reappear on USAF aircraft during the Vietnam War, and this led to a change in tail number presentation. The letters "AF" were added directly above the last two digits of the fiscal year, followed by the last three digits of the sequence number. The three-digit sequence number has a height of the AF and fiscal year letters combined and is sometimes called the "large" component of the tail number. For example, F-4E serial number 67-0288 had the tail number 67(small) 288 (large). This could of course lead to confusion, since aircraft 67-1288, 67-2288, etc would have exactly the same tail numbers as 67-0288 under this scheme. This would not ordinary cause a whole lot of difficulty unless of course some of these larger serial numbers also happened to be F-4Es (which they were not). Unfortunately, the system was not always consistent--for example F-4D serial number 66-0234 had a tail number that looks like this: 60(small) 234(large).

So, '4' represents the second digit of the finacial year, and 1823 gives the sequential number. The aircraft appears to be a F-100 Super Sabre. From f-100.org, the actual serial number appears to be 54-1862, a F-100C-20-NA model.

What's the big "LA?"

Your description of the 5 digit tail number does not match your quotes.  The quote says they used the last 2 digits of the fiscal year and the last 3 of the sequence number.

@TomMcW: Tailcode for Luke AFB

And all that is meant to confuse enemy fighter pilots...

@casey The last part of the quote says that there are some inconsistencies. This is one of them. See this thread about F-4

They are tail codes and indicate the unit(s) the aircraft are assigned to.
In general the Air National Guard units will use their state's two-letter abbreviation.  Others will use something related to the base name (EG for Eglin AFB) or their mission (OT for operational test).
This Wiki provides some data.
An up to date list is available in the Air Force Magazine's annual AF Almanac (June 2017). You can access it online at Air Force Magazine. (Free. Registration required.)


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When do I have to hold during an instrument procedure?
Trying to stay fresh on instrument regs, and I'm reviewing when you are able to bypass a procedure turn. I'm reading that if you perform a teardrop entry for a hold, you may. Does that mean you have to do the entire hold before proceeding the approach when you do a parallel entry?

Can you provide the reference for where you read that?

It was from an online document my cfi showed me.

In that case, yes, the "teardrop" in your question and my answer is not the same one that you do when entering a hold. You might want to edit the title of your question to reflect that.

The rule of thumb is overfly the holding fix twice.  The first time cross it fly the proper entry and the second time you pass it you are on course and continue with the procedure.

That is a good rule of thumb, thank you.

I suspect you are thinking of AIM 5-4-8 (b)(2) [page 5-4-31], which states:

When a teardrop procedure turn is depicted and a course reversal is required, this type turn must be executed.

If so, have a look at the Instrument Flying Handbook, page 7-31.  The teardrop procedure turn is not referring to the same thing as a teardrop entry into a hold-in-lieu-of-procedure turn, it's something different entirely.


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What is the circular pavement at the end of a runway called?
What is the circular pavement at the end of a runway called where aircraft turn 180 degrees to then backtrack? Is the term runway turning bay appropriate for that?
The problem is that there is a special NOTAM at our aerodrome for big aicraft (more than 75 tons of weight) to turn not on the runway but only in this adjacent part, and with maximum radius due to fragile asphault pavement.

Are you referring to a turn pad?

The fact is I'm from Russia. And the term is not used in any official documents. And sometimes our controllers have misunderstanding with the pilots isung this term while giving instructions for RW vacation. Is it used world wide?

ATC will rarely refer to this term. They will just advice the pilot to "backtrack"

Yes, I know it. But still the problem exists. Some pilots do no follow that NOTAM causing much problems to the aerodrome service while repairing asphault after the landing especially in hot weather. Anyway the controller is not responsible for the RW conditions and he is not to blame.

That’s what it’s called in the Eurocontrol Controller Lexicon and in FAA NOTAMs in the US.

It is called the turn pad. This area(pad) is usually located at the thresholds of the runway, where no taxiway exists, so in order for the pilots to make a full-length takeoff, (or taxi to the Apron) they have to backtrack amd make a U-turn on there. Gernerally speaking, these pads exist on small airports. You can see the turn pads at the 2 thresholds of the runway. Skiathos Airport, Greece
Source

Thank you for your comment. Our airport is small indeed)


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What is the appropriate airfoil config for Raked Wingtips?
I'm doing a research about wingtip devices and while I'm searching about raked wingtip, I've wondered what is the best airfoil configuration for it?
Should it be the same as the whole wing?
My study is for application on aerodesign models that should have a low weight and carry a lot of weight.


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How do the linearised equations of motion work?
I am reading this book: "Flight Dynamic Principles" by Cook, second edition.
You can read it here:
https://aerocastle.files.wordpress.com/2012/04/flightdynamicsprinciples.pdf
First, go to the page 76, read the sentence:

Further, the only significant higher order derivative terms commonly encountered are those involving $\dot w$.

Why is the only $\dot w$ involved here? the $\dot u$ and $\dot v$ have the same roles, huh??
Second, same page 76, section 4.2.3, the sentence:

The assumptions applied to the aerodynamic terms are also applied to the control terms thus, for example, the pitching moment due to aerodynamic controls may be expressed.

And you can see the equation (4.32)

it is totally different from aerodynamics terms equation..why is that?. Why are moments not dependent u, v, w, and p, q, r like aerodynamics terms.
Lastly, look at the example 4.2 at page 80, what is the meaning of this example? where do the values of dimensionless longitudinal derivatives at page 81 come from? What are they? The book said seeing the appendix 2 at page 413. Now go to the page 413, where do these multipliers come from?

Please avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question: https://aviation.stackexchange.com/help/how-to-ask

@Federico, the last question should be removed, I'd like to get explainations about other questions, that's really matter to me.

@J.Hougaard ok, I see, I have removed some questions.

Um..it's a bit of a counterintuitive and hard to visualise field of aeronautics. There are six degrees of freedom (if we assume that the aircraft is rigid) that need to be transformed from aircraft axes into earth axes. And since we're looking at aerodynamic stability, we need to consider wind axes to introduce disturbances: if the aircraft moves as an effect of the disturbance, the relative wind changes.
Since we're working with transformation matrices, we can only solve these analytically if there are simple multipliers in the matrix, as soon as there are trigonometric terms such as sines & cosines introduced, we'll need to use numerical methods. So we linearise by looking at small disturbances only, and set $cos(\phi)$ = 1 and $sin(\phi)$ = $\phi$. Usually OK from a body axis perspective, since stall occurs at 15 degree which is a small enough angle. But..
..to make it all even worse, it is one of the few remaining bits of engineering where the dark art of quaternions are used, since when the nose is pointing straight up some of the Euler angles are undefined and we need a fourth dimension to provide continuity.
I reckon if you're interested in this book, the only prior knowledge you need to have is the realisation that it is going to be complex. What has always worked for me is just taking the results at face value, start to work with it to gain experience, then look it up again so that the context is much clearer.
The book does indeed seem to be a bit laborious to read. What they're saying with the statement on $\dot{w}$ is that in the end result, the linearisations and simplifications are justified, in that no big inaccuracies occur if effects of $\dot{u}$ and $\dot{v}$ are neglected. Effects of $\dot{w}$ are significant though and do need to be considered, which the authors do in the rest of the text.
Equation 4.32 is the most generic statement there is on moments - what is says is: the total moment is (how the moment changes with a variable) times the variable. It does not yet consider what the cause of the moment change is.

Thank you so much, I have deleted some questions and keep the important ones, please forget the deleted ones and take a look again at the remaining questions. I really appreciate your answers.

Quaternions are gaining in importance. The Euler angles are defined over all rotations, only when one rotation is close to 90°, you might get gimbal lock. Quaternions avoid that and need fewer operations to calculate a transformation, so they are used everywhere where signals from inertial sensors are involved. And with cheap MEMS, those are popping up almost everywhere. Some of them output their signals already in quaternions.


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What's the story behind U-2 flying from aircraft carriers?
This video from the CIA YouTube channel shows U-2 aircraft launching via catapult and trapping with a tailhook:

The description only offers this:

After stopping U-2 flights over USSR in May 1960, the IC looked for new ways to use this unique reconnaissance asset. One idea was to modify the U-2 to fly from US Navy aircraft carriers.

What motivated these experiments? Were they successful? Was the plane ever used operationally from a carrier? What would a mission objective be?

It doesn't look like it's using a catapult, just launching the old school way.  Don't think it would have needed one and I'll bet the structure couldn't take cat launches anyway.  That might have been one of the problems with using it as it would need an awful lot of deck area and would probably take the carrier out of action from doing its normal duties.

The wings on a U2 seem so long that I find it shocking that they can fit one on a carrier deck. Obviously, the plane is much smaller than I envision. I've never seen a U2 in person, so I have no sense of the scale, but I've been on the Intrepid docked in NYC.

@FreeMan the U-2 isn't all that big, but it was a very tight fit on that carrier deck.The carriers used are the Kitty Hawk class carriers, which are quite a bit larger than Intrepid (their flight decks are at the widest point almost twice as wide as that of Intrepid for example).

Thanks for the info, @jwenting. That would have be some high-precision landing on a moving carrier deck. Far worse than a modern fighter!

From Wikipedia (emphasize mine):

At one time, in an effort to extend the U-2's operating range and to eliminate the need for foreign government approval for U-2 operations from USAF bases in foreign countries, it was suggested that the U-2 be operated from aircraft carriers. Three aircraft were converted for carrier operations by the installation of arrester hooks, and carrier-qualified naval aviators were recruited to fly them.
It turned out to be possible to take off and land a U-2 from a carrier. Testing in 1964 with the USS Ranger and in 1969 with the USS America proved the concept. The only operational carrier use occurred in May 1964 when a U-2, operating from USS Ranger, was used to spy on a French atomic test in the Pacific.
In 1969, the larger U-2Rs were flown from the carrier America. The U-2 carrier program is believed to have been halted after 1969.

It also provides the following resources:
http://www.kristinhillartist.com/FishHawk_article.html
https://theaviationist.com/2015/06/28/u-2-carrier-operations-story/

Could you summarize the contents of those links? It would improve your answer and help combat link rot.

@AEhere I believe the snippet from Wikipedia already does that

We have different standards for summary depth then :)

@AEhere That's also what my teachers used to say ;)


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How to calculate optimal prop diameter, pitch, torque and power coefficient given required thrust?
this is my first post here, so bear with me if this isn't the right place. I'm coming here from Stack Overflow, and this seemed to be the most relevant Stack Exchange for my question.
So, I'm building a multicopter (quadcopter, preferably, due to it's relatively simple design) on a scale that's more-or-less never been done before. I've decided to funnel all the money I made over the summer into this project, and I've just begun the planning stage.
I've worked out that I need about 2500 Newtons of thrust: enough to move 180 kilograms (about 80kg for the person and 100kg for the electronics, maybe more) at a rate of ~4.5 m/s^2 more than standardized gravity—13.888 m/s^2 in total, to be specific. I'd need approximately 750 Newtons of maximum force on each rotor, as my experience with building and coding (from scratch) an Arduino flight controller has taught me that the upper motors often need to work much harder during x and z movement than they would during standard y elevation.
Some other notes:

I'm pretty sure that π * diameter-in-cm * rpm / 6000 must be <340.29 (Mach I). Maybe I should be using a turbofan? Especially considering the next note...
The diameter of the rotors shouldn't exceed 30cm for convenience purposes. I.O.W. it can't be too big or else lugging it around would be a hassle.

Fuel source will (hopefully) be batteries, most likely an array of LiPo cells in series and in parallel (probably something like 10x10), each cell containing about 10,000mAh.

I struggle to continue from this point. I haven't the slightest idea as to how to pick a prop design that is most efficient for this project. My question for Aviation is this:

Given a required maximum sustainable thrust of 750 Newtons, a mass of about 180kg, and the assumption that maximum velocity of the craft is slow enough that air resistance and other drag is pretty much irrelevant...
How would I be able to calculate the optimal prop diameter, pitch, Kp (power coefficient), Kt (torque coefficient), as well as optimal number of blades and optimal manufacturing material? Or, would a turbofan be more optimal?

I wouldn't be surprised if your first thought was something along the lines of "this is ridiculous." Some may even suspect me of being a troll. I can assure you, I am highly committed to this project. My flight controller is insanely stable, and I believe it would be worthwhile to test its abilities on a build that is more heavy, powerful, and top-heavy than most multirotors ever built.
Could you guys point me in the right direction?

Have you looked at off the shelf props? It would probably be a lot easier.

Have you seen this answer?

How would I be able to calculate the optimal prop diameter, pitch, Kp (power coefficient), Kt (torque coefficient), as well as optimal number of blades and optimal manufacturing material? Or, would a turbofan be more optimal?

Optimal prop diameter is simple: the largest you can accommodate = 30 cm. Disk area A = 0.07 m$^2$
Optimum number of blades: as few as possible, let's start with 2.
Use ducted rotors for a more vertical alignment of the rotor tips.
The quadcopter has horizontal rotors. Tip speed should not exceed 0.8M = 270 m/s which equates to $\Omega$ = 570 rad/s = 5,520 RPM
We have a prop diameter, RPM and thrust, now we need to determine power P and torque Q to drive the prop. We'll do so using expanded momentum theory for the hover, like in this answer.

For a rotor with solidity ratio $\sigma$ = 0.1, the thrust coefficient $C_T$  is maximum 0.01, let's use a safety margin of 20% and take 0.008. Then the maximum thrust for this rotor becomes:
$$T = C_T \cdot \rho A (\Omega R)^2 = 0.008 \cdot 1.225 \cdot 0.07 \cdot 270^2 = 50N$$
We need 15 times this thrust! In order to verify the value of $C_T$ there is another graph in Leishman that relates $C_T$ with blade-pitch angle. It turns out that $\sigma$ = 0.01 is at a blade-pitch angle of about 12 degrees, we cannot go much higher than that. Neither can we increase tip speed, our only choice is disk area.

$$A = \frac{T}{ \rho \cdot C_T \cdot (\Omega R)^2} = \frac {750}{1.225 \cdot 0.008 \cdot 270^2} = 1.05 m^2$$
You need four rotors of 1.2 m in diameter, with a solidity ratio of 0.1. With the $C_T$ of 0.008, we find a corresponding $C_P$ of 0.0007, which results in
$$P = C_P \cdot \rho A (\Omega R)^3 = 0.0007 \cdot 1.225 \cdot 1.05 \cdot 270^3 = 17.7 kW$$

This is a very useful answer also for somebody contemplating building a virtual person-carrying multicopter for a flight simulator, thanks...


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Can thrust reversers be set to automatically activate on touchdown?
Is there a switch on the instrument panel that will set the thrust reversers to activate on touchdown like the autobrake? Or is using the thrust levers the only way to activate them?

Can it be done? Yes. Is it done? No. The consequences of unintended operations are serious.
To the best of my knowledge, no aircraft has the option set automatic thrust reverser. Using the levers are the only way to operate them. In fact, most of the design efforts have gone the other way- to ensure that thrust reversers are not deployed inadvertently.

In most aircraft, the Reverse Thrust Levers can be raised only when the Forward Thrust Levers are in the idle position. The thrust reversers have separate levers in front of the engine controls, which are prevented mechanically from operating otherwise.

Source: bloginblack.de

There are sensors installed in the engines which auto-stow the thrust reversers in flight.
The design philosophy of thrust reversers is that it is better to not deploy them when needed rather than deploy them when not needed i.e. they are designed to fail.

The main reason for such a design philosophy is safety. Any uncommanded deployment of thrust reversers in any phase of flight can have serious consequences.

Takeoff- If the trust reversers are deployed in one engine before $V_{1}$, the aircraft will veer off the runway. If it is deployed after $V_{1}$ and before $V_{2}$,the aircraft cannot achieve $V_{r}$ required to initiate rotation.
Flight- Deployment of thrust reversers during flight can lead to controllability issues.
Landing- Deployment of thrust reversers during landing practically eliminates the option of rejected landing.

Because of these reasons and reliability issues with thrust reversers, there is no option for automatic deployment of thrust reversers.

You also don't want them kicking in during a go-around which includes the wheels touching the runway and weight on gear.

If you have the spoilers armed don't they automatically deploy on touchdown? Is it that spoiler deploymentjust doesn't have such serious effects as TR do?

The main effect of the spoiler deployment is that it 'dumps' lift and as a result, the weight is transferred from wings to the undercarriage. Deployment of thrust reversers, on the other hand, causes serious thrust imbalance (The difference in thrust between engines will be more than 100% of single engine thrust). It is practically not possible for the pilot to control the aircraft in such an event.

@TomMcW, spoilers are also extended and retracted very fast and with mimimal risk of being asymmetric. Thrust reversers take much longer and there can be significant variation causing asymmetry.

Asking a related question.

Should "rejected takeoff" be "rejected landing"?

Yes. Edited. thanks.


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How often are slats used on airliners?
Are slats only used when there is a short runway or on all occasions?

On all occasions when flaps are deployed.
Slats are a necessity when the wing uses slotted flaps or Fowler flaps for maximum lift. Those flaps cannot reach over the whole span of the wing to leave room near the wingtips for ailerons.
Once the flaps are extended, they increase the incidence of the wing along the flap span. This leaves the outer wing at a lower incidence, but in the vortex field of the inner wing. This vortex field induces a high local angle of attack over the whole wingspan, which would produce a local stall at the wingtip, where the ailerons prevent the use of slotted flaps. This stall would in most cases be asymmetric: One wing tip loses lift while the other barely manages to get along with the high angle of attack. The result is a strong rolling moment which will even increase once the aircraft starts to roll, because the local angle of attack at the down-moving wing will increase further. At this condition, the ailerons are of little help, so the roll cannot be controlled.

Angle of attack change due to movement (own work)
Now consider when flaps are used most often: Close to the ground, during take-off and landing. Then imagine what happens when the airplane rolls over one wing uncontrollably. To avoid this, slats are very helpful: They give the wing an extra stall margin by shifting the stall angle up.
While the Airbus in your picture uses slats over the whole wing, they are strictly needed only at the outer wing. Adding them ahead of the slotted flaps will increase the maximum lift and reduce the minimum speed over what is possible with flaps alone, so full-span slats (sometimes combined with Krüger flaps on the inner part of the wing) are now standard.

The slats are high lift devices which allow the wings to operate at higher angles of attack. In most of the aircraft, the slats are deployed automatically when the flaps are deployed.
The flaps are deployed to increase the camber of the airfoil seaction, which increases the lift coeffecient (and reduces the stall speed). However, the flaps also reduce the stall angle, so the wings stall earlier (at lesser angles of attack). Better the flaps are in increasing lift coeffecient, more this reduction in stall angle is.

Source: code7700.com
During landing and takeoff, when the flaps are deployed, are the conditions when the angle of attack is high. The addition of slats increases the stall angle, so that the wing angle of attack can be high without any danger of stall.

Source: www.recreationalflying.com
Due to this reason, the slats are used in all occasions when the flaps are deployed (during takeoffs and landings). Actually, the flap/slats are controlled by the same lever so that the slats are deployed whenever the flaps are extended. For example, the Embraer 190 flap/slat control lever looks like this:

Source: www.woodward.com
According to Embraer 190 Flight control System Summary,

Slat and flap motion is sequenced such that slats extend first and flaps retracts first when the motion command requires both surfaces to move.


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What is the small openining on the bottom right of door 4R of an Airbus A321?
While observing taxiing A321 planes, I noticed that they had an open hatch-like opening on the bottom right of door 4R.  I marked it here on a picture I found online.

I could not locate it in the Airbus A321 Aircraft Characteristics manual.  What is it for?  Why was it open?  Does it stay open during flight?

The question What is this device below the door of a 737 and its answer are better than the suggested "What is this square hole for".


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How do I tell if class E airspace extends to surface or starts at 700'?
I am confused about where class E airspace starts in the USA. If it has dotted magenta lines does it start at the surface? If small airport has round magenta circle but no dotted lines does class E start at 700'?

Welcome John. This site covers aviation question from all around the world. When asking a question about local procedures, please remember to mention which country you are asking about, since local procedures change, well, depending on the location. I am going to assume you are asking about the USA, and I have edited your answer accordingly. Please change it if my assumption is wrong.

There's an excellent web page here that helps explain class E.


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Why does a hydraulic system failure increase the landing distance?
Considering wide body aircraft, why do emergencies, related to hydraulic system failure, increase the landing distance?

Landing distance is a function of the formula
Kinetic Energy = 1/2 * mass * velocity²

Any change that will increase kinetic energy will require longer landing distances.  When we land, the kinetic energy needs to go somewhere.  It can be converted into heat with the brakes, opposed with drag from the thrust reversers or deployed spoilers

Higher landing speed will cause an increase kinetic energy that must be converted on landing and thus you will have a longer landing distance.
Braking, thrust reverser or spoiler issues will increase the landing distance because they will not be as effective (take more time) in converting kinetic energy.

In a hydraulic issue, most likely the manufacturer has chosen to fly the airplane at a speed greater than needed for a normal landing (VREF + 20) and will most likely not have the ability to use normal braking.  Most jets use hydraulic fluid to stop the brakes.
In the jets I fly, without normal braking means we use the emergency brakes which are not routed through the anti-skid system so precaution must be taken to not skid the tires.  This all adds up to a substantial landing distance penalty.  Hare the landing distances for some airplanes.

Learjet family: Factor of 3.15
Learjet 45 family:  Factor of 2.2
Challenger 604 family: Factor of 1.7 (braking) times 1.8 (airspeed) for a total of 3.06

Any hydraulic failure will affect the landing distance as most of aircraft controls are operated by hydraulics.

If the high lift devices (flaps) become inoperative (or become degraded) due to hydraulic failure, the aircraft will have a higher approach speed, which will increase the landing distance.
Hydraulics are also used for operating a number of other systems like brakes, ground spoilers and thrust reversers. Any degradation in their operation will increase landing distance.

In most wide body aircraft hydraulics are used to lower flaps, raise spoilers, and in some cases apply wheel brakes. A flaps up landing is going to mean a higher landing speed, no spoilers will mean less drag to slow the aircraft, and not having wheel brakes will mean a much longer roll-out.
Also worth noting is that a hydraulic failure which will impact those systems will probably impact flight control surfaces as well, and landing gear extension, so a longer landing distance is the least of a pilot's worries in that situation.

Aircraft with hydraulically-operated wheelbrakes have a hydraulic brake accumulator in order to provide wheel braking even in the event of a total hydraulic failure; that said, the brake accumulator only holds enough pressure for a limited number of brake applications, so antiskid braking is inoperative if all hydraulic systems feeding the brakes have failed, and this could produce a moderate increase in braking distance (as locked wheels slow the aircraft less effectively than still-spinning ones).


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What factors should be considered when taking private pilot renter's insurance?
I'm just about to start on my first solo and was informed by my CFI that I need to have renter's insurance at a cost of about $180/year.  I looked on AOPA for this insurance and confirmed that the prices is correct if I choose no coverage for "liability for damage to non-owned aircraft".  What are the factors I should consider in making the decision to add/not add this other level of coverage?

Hi.  Welcome to Stack Exchange Aviation.  Unfortunately, this is not on topic and is probably opinion based at best since the answers depend on the attitude to risk of the answerer.

Ignoring what you should and should not have in terms of coverage for your self there are some facts to note about getting gap insurance.
You need to speak with your flight school and ask them what they require you to have as every flight school could be insured differently. For example, when I got my renters insurance I had to have 10K of aircraft damage coverage as the flight schools insurance did not kick in until then. Had anything happened I would have been responsible for the 0-10K worth of damage. In this case you would want coverage for damage to the aircraft. If the flight school has insurance on any and all damage you may not need it on your insurance.


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What is the viability of stacking passengers in an airplane cabin?
I've came across on youtube a new design for stacking passengers in an airplane cabin, that looks at first sight interesting.

What would be the advantages and drawbacks of such a design? Why this is not common in today's airplanes?

Hi Laurent, welcome! The question doesn't seem to be on-topic here, it relates more to the travel.se scope (cabin and passengers). Now usually the passengers limit is that the aircraft must be evacuated in 90 seconds. The more passengers, the more doors are required to achieve this time.

I wanted more technical comments, travel.se is more social. But I'll post the question on both, I'd like to get all kind of expert opinions.

Ugh.  It's bad enough having to contort myself into a seat designed for someone with significantly shorter legs and narrower shoulders than I have.  That attrocity looks like it would add to the fun by requiring me to force myself into something also designed for people with shorter torsos and/or the gymnast class flexibility needed to contort myself into a leaning back seated position in the aisle without toppling over before sidestepping into the seathole.

I don't see this being viable for only a 6.4% seating capacity increase. The amount of extra weight alone would negate the extra passenger seats just in fuel costs.

@DanNeely:  The seat are not "designed for someone...".  The seat is designed to fit the available space; passenger be damned.

To me, it is a huge warning flag that one of the articles attached to the video says, "Though he is a designer, Grégoire is not an industry-insider. He works in the bedding industry and came up with this concept on his own, as a viable solution to today’s limited horizontal cabin space.", but the video (between 0:25 and 0:35) describes the evacuation times and safety features.  I really don't trust an industry-outsider with no aviation experience to design safety-critical components.

@DanNeely Is gymnast class an upgrade from sardine class?

They could just put a metal bar or straps on the ceiling for standing passengers like they do on subway cars :P

@TomMcW The atrocity in the video looks worse than the current veal class standard.

@Laurent Please don't cross-post.

Related: Why don't airlines load their passengers like freight?

Related: Is it technically viable to introduce sleeping berths?.

This is the kind of "out of the box" thinking that leads some people to suggest euthanasia for the alleged thinker.

I see several challenges with this design, both technological and not:

Making that design safe enough will be difficult, the structure you add in the cabin would need to be strong enough to maintain rigidity in a crash. That much rigidity would add weight, and would add loads to the structure
The pod walls will make it hard to get by people in the single narrow aisle. In an open design you can squeeze by people in the aisle, in a walled design you'd have no place to go
This design would greatly limit carry-on storage to only what could fit under the seat in front of you
Parents with small children and families traveling together would have a hard time with this design as there's no more than 2 seats together, and limited space for sky cots
Access to a sick passenger would be restricted
Passengers with limited mobility would have a hard time getting into and out of these pods
Comfort is the biggest problem I see with this design. Anyone in one of those pods is spam in a can with limited visibility and movement. Personally I think it looks awful and I would go out of my way to avoid flying with an airline using it

The problems I can see with that design:

Increased structural weight: all things remaining the same, you will have less payload availability for luggage/cargo.
Cabin servicing you either add an elevated kitchen (more weight) or you have to go up those stairs with the carts every time you want to service the cabin.
Possible claustrophobia those modules look tiny, and the center rows are quite different from a car where you can open the window.
Possibly longer evacuation times you are increasing the passengers, making them lay down more (more time to get up/out of those compartments), and maintaining the same volume. And people will try to get their belongings from under those seats. You will have to demonstrate that this does not adversely affect the prescribed evacuation times.

Now that you have added screenshots, and that I have more time to look at them, I would add that

there is no consideration of the oxygen masks, where are they going to fit? For both bottom and top row there does not seem to be the required space.

The depicted seating configuration wouldn't fit in a typical wide body aircraft.  It would require a jumbo platform, such as the 747 or 380.  A wide body aircraft can only do 2+4+2 seating, whereas this configuration requires another 15" aisle.  Further, this configuration appears to suggest additional walls and structural components that would increase the width.

If you move to a jumbo platform, you find they're already stacking passengers in two levels, so there's no advantage there.
Further, there isn't enough height for the elevated aisleway without significantly impinging on the aircraft backbone.  You may be able to convince the aircraft company to build a widebody with two separate backbones, but that would increase weight, assembly costs, and would limit the ability to route cables, hoses, ducts, and other necessary items through the area above the cabin.
Lastly, you'd have to increase the amount of wiring, lighting, ducting, and emergency equipment to support the additional passengers.  This may involve more than simply space considerations.
This doesn't even begin to approach considerations for claustrophobia, evacuation, loading, and so forth.

The configuration example is intetended to be for a A350.  The show a side by side comparision of a 3+3+3 configuration at 1:50 in the linked video.

BA has nine abreast in economy on their 777s (3+3+3). Air Canada, KLM and TAM have ten across. I don't know if you can really squeeze in this double decker layout but you can certainly get more than eight abreast. (I'm glad I don't travel in economy anymore...)

The video shows the seat-pitch at 42".  Current seat pitch is typically around 30-33".  I'm pretty skeptical that you can increase seat-pitch by 10" and still increase seating, no matter how much seats are stacked on top of each other.
Also, the video shows seating in a 2-2-2-2 configuration, with 3 aisles.  Typical wide-body seating is 2-4-2, 2-5-2, 3-3-3, or 3-4-3 with 2 aisles.  This implies the seats would be even narrower than current seats.  And current seats are already pretty narrow for most average sized people.
Typical wide-bodies have overhead bins inboard and outboard (4 overhead bins per row).  This diagram shows the outboard overhead bins, as normal, but no inboard overhead bins.  There is some small space above the upper-deck seating, but none for the lower-deck seating.
In my estimation, they're cramming more passengers into narrower seats, with less luggage space.
It is an interesting video, but I want to see Numbers and Math to back up the pictures.

For me the maths make sense: if you have two rows of passengers on top of each other, going from 33" to 42" can still increase the total number of passengers, even taking into account the increase in aisles number. AFAIU the width of each seat is the same in the comparison: 2-2-2-2 + 3 = 3-3-3 + 2 = 11 width "units" (assuming seat and aisle approx. the same width).

" I'm pretty skeptical that you can increase seat-pitch by 10" and still increase seating, no matter how much seats are stacked on top of each other." Huh? Increasing the seat pitch decreases capacity by only a third; having an extra deck clearly more than compensates for that.

As @yitzih said, (and it is worth repeating) it is unlikely that seat-pitch would actually be increased by 30%.  Rather, it is much more likely that seat-pitch would remain the same, and 30% more seats would be packed in. :)

I could think of 2 reasons not yet mentioned by the other answers.
1) The "passenger leg room and capacity increased by 6.4%" would turn into "passenger leg room unchanged and capacity increased by 9.3%" or some such thing. If an airline can stuff you in a bit tighter, they will probably try it. So really not much would improve for the passengers.
2) Airplanes are incredibly expensive to build. Many airlines are still using airplanes that are fairly old. This would likely only be possible if the entire airplane was redesigned to fit this which would mean it would only be seen 10 years in the future at the earliest.

Which part of the concept requires the whole plane to be redesigned? Cabins are already designed to be reconfigured for different airline layouts. It may take some work but existing planes should be able to be modified for even the larger parts here.

The seats are not fixed into the cabins; airlines are often re-arranging them and adding and removing seats of different classes to try to optimise their return. Also, every time an airliner goes through a D check the whole interior is removed down to the metal framework.

@Calchas OK, so D-checks become more expensive because there's way more cabin to remove and it would be in bigger chunks.

Another strike against - the lines of sight are obscured.  In an emergency seeing as far as possible is better - both inward and outward.
Similarly, if there were to be a hijack then there's more chance of clandestine preparation out of anyone's sight.  Open spaces with cabin crew circulating works against privacy to prepare.


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Is it OK practice to use one altimeter on QFE and one on QNH (local flight, dual altimeters)?
PPL student, wondering on how this practice is viewed. The aircraft I'm learning to fly in has a small Dynon EFIS which displays horizon, airspeed, heading & altitude. It also has a regular altimeter.
Assuming I'm going for a local flight, returning to land where I departed, is it OK practice to leave the Dynon on QFE and the Altimeter on QNH? This way I don't have to change any settings.

I curious why you think that using dual altimeters for what they are intended for might be a problem?

Are you in a place that uses QFE for terminal operations on a regular basis?  (Standard practice is to use QNH throughout, except in a few oddball parts of the world where QFE is used in the terminal area...)

I'm wondering as I'm coming up for my skills test soon. It's maybe not so clear cut as one altimeter is embodied within the EFIS. The airfield I fly from is at around 400ft AMSL, so QFE is used.

I would turn it the other way around. Assuming the Dynon EFIS is your main flight instrument I would dial in QNH or QNE (depending on your altitude). Common practise is to always have the second altimeter set to QNE (1013.25hPa; 29.92inHg) but if you do not need an altitude reading in Flight Levels it's fine if you set up one altimeter to QFE.
But remember: Even using this practise you HAVE to change the settings. QFE and QNH are both depending on the local pressure and therefore change pretty often. If you are on a cross country flight you then have to change both altimeters to different settings in order to have a correct altitude and a correct height readout.
Also make sure that you always use the same altimeter for altitude and the other one for height so you won't use faulty values from the wrong altimeter!

I'd emphasise that last point. No quicker way to fail your test than using the wrong one.


text:
How do I log simulator time in my logbook as a CFI?
I'm a CFII at a 141 flight school, and when I give instrument instruction in our AATD flight simulator I'm kind of confused on how to log it. Should I log "As Flight Instructor" time even though it's not a flight? (My logbook has no "Dual Given" column which would make more sense.
Also, am I able to log "Flight Simulator" time? Even though there's only 1 yoke in the simulator, which I am not manipulating.

Buy a second logbook
Here's one that costs $11
As a CFII who had exactly the same problem that you did, I can tell you that this is the easiest and simplest way to keep your simulator dual given and your airplane dual given separate.  You just log all of your simulator time as if it was airplane time, but in a simulator.  So, flying a sim that emulates a multi-engine airplane? Airplane Multi-Engine Land column!  Put the student in the soup?  Actual instrument column! Record the serial number of the AATD in the "Aircraft ID" column and you're all set!
But it would be simpler to have just one logbook...
In that case, see if there's an unused column in your logbook that you can cross out and relabel as "simulator dual given".  Airplane Single-Engine Sea works well for this.
Isn't there some kind of technology that could solve this problem?
Sure is!  Electronic logbooks are the bee's knees.  Try Zululog, I don't use it but it's free so if you hate it all you've lost is some time.  Foreflight has a logbook option too. I don't like it (it seems lightweight to me) but you might.
Can I log flight simulator time?
Technically you can log anything you want, including passenger time, chair flying time, and time spent in the hangar arguing about taking off from a treadmill.  The question is whether or not that time is valuable toward future certificates, ratings, or employment.  Dual given as an instructor in a simulator is, sadly, not at all valuable.  No one really cares and you can't use it toward any certificate or rating that I'm aware of.
Which is why you want to log your simulator instruction in a separate logbook; assuming you're not planning to instruct for the rest of your life like me, when you go in for interviews you'll be able to just bring your aircraft logbook and leave the simulator one at home.

+1 for time spent in the hangar arguing about taking off from a treadmill.

+1 This answer is perfectly simple and thus simply perfect.

The simple answer is yes, log it as instruction given, but not flight time.  Some logbooks provide for ground instruction given, and flight instruction given, but most instructors log it as simulator instruction given.  Including the instructors at Flight Safety.


text:
Can structural damage be detected or predicted using historical data?
Can software simulations and structural health monitoring techniques accurately predict damage occurrence in aerospace structures using historical data(stiffness,damping and vibration measurements over a considerable period of time)
or
Are these techniques more suited to real time damage detection rather than damage prediction ?

For eg. SHM techniques such as parameter estimation using Frequency Response, or Non Destructive Inspection.

I'm not sure it can accurately predict either. There are a lot of software packages out there that can model structural damage, but I don't know of any real-time damage detection system in use...

Sounds like a research project (e.g. for studying PhD, anyone?)

This is the basic principle behind predictive maintenance in general. In the aviation industry, adding hundreds of cheap wireless sensors will help in this direction.

Since few years, flight data is used to improve predictive maintenance.
This Big Data approach is apparently very popular among airlines.
But structural damage must still be evaluated by hand (and torchlight) from reports.

Yes it can be done. However, with the advent of technologies, you can also use the real time updates of the monitored system to understand it's health. In some cases where the historical data is not available, it becomes important to assess the structure's condition based on real time updates. I feel the following links could be of interest:

https://journals.sagepub.com/doi/full/10.1177/1475921718760483
https://www.sciencedirect.com/science/article/pii/S0888327017304612

"Links are not a substitute for including information in your answer itself, and links should always be directly relevant to a part of your answer." If you could elaborate on how it can be done this might be a much better answer. Also, it would be nice to disclose you are the first and second author on those articles you linked, otherwise this may be flagged as spam.


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How to understand "Stage length, for payload calculations includes 85% wind"?
Reading "Long Range Aircraft-AEA Requirements".
In appendix, Para 1.2 "Definitions and specifications", the definition for "Stage Length" states

Stage length [...] for payload calculations includes 85% wind.

What does that mean?

The document AEA Requirements Long Range Aircraft is related to airline fleet planning, and the calculation of the fuel needs. Note that it is dated Dec. 1987. More on airline fleet planning.
85% wind
For this planning the document from the airlines association recommends to assume the wind that has a probability to occur of 85%. That means: assume you will find this wind on your route 85% of the time. The wind force itself is determined talking into account statistics for the regions overflown.
Stage
The flight profile is provided on the document itself, defining "stage" as start of climb to end of descent, excluding initial climb:

Planning profitability
Knowing how much fuel will be required and by deduction how much payload can be transported allow airlines to estimate the airline costs and revenues on a given route with a given aircraft. This is important for planning aircraft acquisition and replacement, as well as the route catalog.

Stage length is basically the average length of the flight (see mins' answer for a specific definition).  Average stage length is important because it greatly effects the maintenance and fuel costs for the airplane.  The shorter the stage length, the higher your overall costs will be for the operation of the airplane (and vice-versa, of course).
In order to estimate the stage length, the following information is needed:

Routes which will be flown
Performance information for the aircraft
Average winds which will be encountered during the flights

The 85% most likely refers to the Boeing 85% wind data, which is proprietary data produced and sold by Boeing and includes world-wide wind and temperature data at various flight levels and seasons, with statistical reliability between 50% and 99%.
This means that the wind values which are used for the stage length calculation will result in a flight time equal to or better than the result 85% of the time.

I wasn't aware of the source of these figures. It's also worth mentioning your related question: Where can Boeing wind data be found?.


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Would the wings of a Boeing 787 be snapped off in the same turbulence in which a DC-8 lost an engine and parts of a wing?
From forbes.com:

In 1992, a DC 8 cargo aircraft suffered turbulence so severe over the Front Range of Colorado’s Rocky Mountains that its left outboard engine was completely ripped off as well as some 12 feet of its left wing’s leading edge. Mercifully, the pilot was able to make an emergency landing at Denver International.

If a 787 was put in the same turbulence as the DC-8, would the wings snap off? The DC-8 is from the '50s while the 787 is a new aircraft.

12 feet of its left wing’s leading edge — that's not the same thing as the wing 'snapping off'. The wing was overloaded, and a portion of it was damaged and torn from the airframe, but the DC-8 in question did not lose any span. See the NTSB report: https://aviation-safety.net/database/record.php?id=19921209-1

Still classifies as wing damage. There's a photo of BOAC Flight 911 where the wing folded before the plane crashed (also due to turbulence) taken from a person on the ground who was filming the plane flying over Mt. Fuji.

Damage, sure. You are specifically asking if wings would "be snapped off", though. If you're actually asking if the 787 would suffer the same damage as the DC-8, you need to rephrase your question.

@egid I read the question as "would a modern aircraft be doomed by turbulence that an old aircraft survived (just)"

It's very likely that the 787 would have less problems with turbulence than the DC-8 did.
The wings of the Boeing 787 are more flexible than the DC-8, and that flexibility will damp the immediate impact of turbulence. More important, the Boeing 787 has a gust alleviation system that reacts to turbulence by counteracting the induced accelerations using the control surfaces.
Note that the aircraft certification standards have changed a lot since the DC-8 was certified. Originally the focus was very much on the maximum g-forces the wing could sustain, but this is not a very good measure for turbulence. The g-forces encountered in turbulence are the result of a combination of the turbulence itself and the aero-elastic response of the aircraft. Using a more flexible wing and gust alleviation systems will result in a much smoother ride (less g-forces) than a traditional very rigid wing.
Currently the certification standards define, in addition to a required g-force, the characteristics of the turbulence that the aircraft has to sustain. For example, see the FAA's regulation for large aircraft, FAR Part 25, Sec 25.341.
This takes into account a range of characteristics of turbulence that can be encountered as well as the dynamic response of the aircraft to that turbulence.
Apart for aerodynamic and structural differences between the DC-8 and the Boeing 787,  better understanding of (mountain wave) turbulence, better weather prediction, better reporting of turbulence by aircrew (simply because there are more flights) and better weather radars on aircraft have reduced the risks of encountering turbulence since the DC-8 era.


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What does the "DO NOT USE FOR NAVIGATION" indication mean?
Sometimes when I'm browsing IAC charts online I find a "DO NOT USE FOR NAVIGATION" notice printed on the chart. Not always though.
For example, have a look at the chart for Queenstown RNAV (RNP) Y RWY 05.
See the notice there?

I have always wondered why do procedure designers put these notices on their charts. I find it almost contradictory, since I think these charts are the best source of information that an aircrew can have to navigate/maneuver. Isn't it ironic?
I'm sure I must be missing something.
Can anybody shed some light on this?
PS: These are not SIM charts. These are real charts from the AIP.

I suspect these notices appear on the online versions of charts, because the online versions are not guaranteed accurate. The notice probably doesn't appear on the paper version.

Can't say authoritatively as I'm not familiar with NZ rules but in the US, IFR charts are published every 28 days, thus any chart older than that would be 'Not for navigation'. This one was effective 9 Nov 17.  Also, redaining the NZ AIP web site disclaimer, the charts are for 'personal use'. This approach is restricted in that it requires GE Aviation approval as well as CANNZ RNP-AR approval. Basically, this is a PBN RNAV approach for airliners with a GE Aviation FMS. So there's no real reason to keep a valid copy on the web site since most of the public can't use it.

It means that you shouldn't use it for navigation.

Queenstown NZ is an interesting area - as you can tell from the chart!     https://www.youtube.com/watch?v=7mxmFCw-Dig    nose video of a landing.

Unless it's an obsoleted procedure chart, it usually means that it's not complete.  The example you show has only the features pertinent to that approach, and its missing (for clarity) the features needed for any other aviation in that area.
You must use a sufficiently complete chart for navigation; the approach diagram is supplementary to your navigation chart.

What exactly you find missing and which is present at other approach plates to the very same aerodrome like http://www.aip.net.nz/pdf/NZQN_43.1_43.2.pdf ? What kind of navigation would you expect from an IFR approach plate?

When an aviation chart is marked with "DO NOT USE FOR NAVIGATION", it means that ... umm ... it should not be used for navigation.
The question is why it should not be, because it appears that the chart/map is very accurate and hence it is thought that it can provide details for navigation.
There are several reasons:

A newer version might be available and hence making older versions obsolete.
It may not be according to scale and can cause confusion.
It may not show air routes.

On the contrary, a chart can be used for navigation when it has the following (yes, AOPA said it):

topographic features
hazards and obstructions
navigation routes and aids
airspace
airports

If these reasons are true, why the RNAV RNP approach has it, but the VOR DME approach chart http://www.aip.net.nz/pdf/NZQN_43.1_43.2.pdf ?

I do not believe the reasons stated in other answers. The only difference between this approach plate and other approach plates for the very same aerodrome in the same AIP like this or this (also RNAV, but RNAV GNSS, not RNP) is the type of the approach. The level of details of the map, for example, is exactly the same.
One needs special equipment and a special approval for this approach and cannot just fly it according to the map or select it in a normal Garmin.
The plate misses something important and it is NOT the details of the map. These are the actual minima to be used for the approach (I do not get what other navigation some suggest other than the approach for which the map only exists...). Notice the important notice:

Minima figures are indicative only. See CAANZ RNP-AR operator approval for specific procedure minima.

So this approach plate is not enough, more information is needed to properly perform the approach. Not to do other unspecified navigation, no-one would do that, but to fly the approach (or the associated missed approach procedure).
The AIP (ENR 1.3) also says:

1.4.2 Special RNP-AR approach and departure procedures are designed to criteria that differ from ICAO specifications and have been approved for use by CAA. These procedures are only available to operators with contractual arrangements with the procedure design organisation. Tailored instrument approach charts and navigation data-cards are only provided to contracted organisations. CAANZ approval is also required.
1.4.3 The Special RNP-AR procedure charts are annotated with the applicable restrictions. They are published for the use of ATC and for situational awareness by other aircrew and are not available to be used for navigation purposes.

The current version of this approach chart does not have the "do not..." placard, and is otherwise essentially identical as for the content referred in this answer, so this answer is not entirely correct.

@ymb1 Oh, indeed, my mistake!

In some countries, administrative and legal reasons require that label, because maps officially usable for navigation may need

process used for completion including various warranties, for example:

included map layers collected from their respective sources can be no more than 3 months old
the map got reviews and approvals prescribed by the process – all documented, with clear responsibilities
by adhering with the process, the map received official certification and then catalogization etc.

The same company can produce ad-hoc maps from similar sources, of similar quality which still did not go through the entire (quite expensive) process and therefore they are mandatorily marked as "DO NOT USE FOR NAVIGATION" which is also connected to various legal implications.
So such a label might not inevitably mean that the map is missing something. Even after closer look, it can appear 100% complete. But it should not be used as official navigation aid. For example, if an insurance event will occur where navigation can be at least slightly involved (or even theoretically), finding out that such a map was used for navigating will give aces into hands of the insurance company.

In addition to the other excellent answers, because the publisher expects to be compensated for creating the charts.  In other words, they don't want you downloading free stuff, they want to sell you approach plates needed for actual flight.  They put this tag on any print or electronic version promulgated for training or general reference.

Right, in addition the publisher is not the CAA itself, but a private company Aeropath, owned by Airways New Zealand, the national ANSP. They have obviously an agreement.

The copyrights are mentioned in the chart, and the copyright holder is CAA, so this chart was free.

The simple answer is that the chart is or will become outdated. As a pilot you need to have current charts when flying.
The marking shows that the publisher does not take any responsibility for the currency or accuracy of the free chart found on internet or in training material.
You can buy sets of current charts and subscribe to updates to always have a current set. Not to promote this here, but one example of company selling charts is Jeppesen. http://ww1.jeppesen.com/documents/aviation/business/ifr-paper-services/glossary-legends.pdf

The really simple answer is that the chart does not contain everything a pilot needs to know to navigate safely. That could be because it is missing features for clarity, is a training tool, or, as is this case for Queenstown, because pilots must have additional certifications in advance. It is very rarely because a chart is out-of-date since why would anyone update a chart that is out of date?
Whatever the reason for the warning, a chart with this prohibition on it is intended to be used to assist a pilot who already knows whatever it is they need to know (as highlighted on this one with the text boxes in the lower left corner), but can not be used safely by anybody who does not already know how to navigate here.

authors: Vladimir F Героям слава